Elimination of twists and bends from elongated cold roller formed members



OLD

July 22, 1969 K. A. ELLIS ELIMINATION OF TWISTS AND BENDS FROM ELONGATED C ROLLER FORMED MEMBERS 2 Sheets-Sheet 1 Filld Feb. 5, 1966 July 22, 1969 K. A. ELLIS 3,456,471

ELIMINATION OF TWISTS AND BENDS F ELONGATED COLD ROLLER FORMED M'EMB Filed Feb. 5, 1966 2 Sheets-Sheet 2 ll'xc &

United States Patent 3,456,471 ELIMINATION OF TWISTS AND BENDS FROM ELONGATED COLD ROLLER FORMED MEMBERS Kenneth A. Ellis, Evansville, Wis., assignor, by mesne v assignments, to Varco-Pruden, Inc., Pine Bluff, Ark., a corporation of Delaware Filed Feb. 3, 1966, Ser. No. 525,282 Int. Cl. B21b 15/00; B21d 13/04; B23p 17/00 US. Cl. 72177 6 Claims ABSTRACT OF THE DISCLOSURE Lengthwise curvatures and twists are eliminated from roller formed Z- and L-section elongated members by crimping the member along a marginal side edge portion thereof to compensate for elongation of said portion during forming, the crimps decreasing in depth laterally inwardly from said edge to zero at a predetermined lateral distance therefrom.

This invention relates to metal structural members of the type, which are roller formed while cold from flat strip stock, to have bends .along lines parallel to the longitudinal side edges of the member; and the invention is more particularly concerned with the elimination of undesired twists and lengthwise curvatures which have heretofore characterized such members produced by the cold roller forming process.

It has long been known that the cold roller formation of relatively heavy gage metal channels and similar metal structural members from straight, flat strips of stock usually produces pieces that are curved or twisted along their lengths. Generally, the undesired curving or twisting is greatest with pieces of the heaviest gages, being very marked, for example, in 12, 14 and 16 gage pieces intended for relatively heavy structural applications. In the case of a U-shaped member having flanges substantially equal in width, the piece is bowed all along its length in the direction away from the edges of the flangesln the case of Z-section members an undesired curvature exists along both side edges of the piece and is in opposite directions along the opposite edges of the member to produce the net effect of a marked twist along the length of the member.

Heretofore the presence of such twists and curves in elongated metal members that are cold roller formed from flat strip stock has been accepted as inevitable, and heavy roller formed structural members have therefore been used only to a limited extent.

In cases where straight, uncurved members had to be produced from strip stock, they were often formed on a bending brake, but use of a brake in such an operation was time consuming, awkward and costly, and the member produced thereby was substantially more expensive than if it had been cold roller formed to the same size and shape.

Various attempts have been made to prevent the undesired curves and twists that appeared in cold roller formed members, but heretofore such efforts have been generally unsuccessful, particularly with heavy gage particularly, to provide a very simple method of straightening such a member after it is formed, to remove all twists and curves therefrom.

It will be apparent that it is also an object of this invention to provide a cold roller formed member per se which is substantially straight and untwisted along its length.

The invention is based upon the discovery that the twist or curve in a cold roller formed member of the character described results from elongation, during the forming operation, of one or both marginal edge portions of the member relative to the remainder thereof. Such elongation of the edge portions occurs just as the stock is passing into the bite of the forming rollers, while it is undergoing bending. As the stock is being bent to the desired shape, one or both marginal edge portions of the strip are subjected to substantial lengthwise stretching, owing to the fact that the marginal edge portions undergo the greatest change of position during roller bending and must therefore undergo a relatively greater elongation than the rest of the stock in order to accommodate the difference in shape between the formed portion of the stock that is in the bite of the forming rollers and the unformed portion that has not yet entered their bite. Forming the member in a succession of roller passes cannot substantially alleviate the problem because the small stretches that are imparted to the edge portions at each bending operation are cumulative and produce about the same amount of edge elongation as would be effected if the same degree of bending were accomplished in a lesser number of passes.

Because the formed member is longer at its side edges than it is along its centerline, there is a severe unbalance of internal stress forces in the member. In a U-section channel the relative elongation of the edge portions causes a bowing along the length of the member in the direction away from the edges. In a Z-section member, in which the relatively elongated opposite edge portions are offset to opposite sides of the plane of the web or longitudinal center zone of the member, the lengthwise bowing due to the relatively longer edge portions produces a marked twist along the length of the piece, readily perceptible even upon casual inspection.

According to the present invention, a cold roller formed metal member is straightened by crimping its relatively longer edge portions to the extent necessary to elfect such foreshortening of the edge portions as will bring their projected lengths into equality with the length of the remainder of the member, the sinuosities produced by such crimping being of maximum amplitude at the edge of the member and substantially uniform along the length thereof, but tapering laterally inwardly from the edge, consistently with the greatest elongation of the member being at its edge, and decreasing to the vanishing point at some predetermined lateral distance from the edge.

Thus it is another and more specfic object of this invention to provide a simple and inexpensive method and means for foreshortening the longitudinal edge portion-s of a cold roller formed elongated member, to bring the projected lengths of such edge portions into equality with the length of the central portion of the member and thereby remove from the member any twist or other undesired deformation that it might have as a result of the cold roller forming operation.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel method and construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiments of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete ex- I I FIGURE 3 is a more or less diagrammatic perespective view illustrating the formation of a Z-section channel member from flat strip stock by means of forming rollers;

FIGURE 4 is a more or less diagrammatic perspective view illustrating the practice of the method of this inven tion on a Z-section member by means of crimping rollers; and

FIGURE 5 is a perspective view on a larger scale of a portion of the member shown in FIGURE 2, particularly illustrating the crimp or sinuosity in its edge portion.

through their bite, or they can be freely rotatable idlers through which the member is propelled by suitable drive rollers or by the power driven rolls of the roll forming machine. In any event, it will 'be understood that the two crimping rollers 14 are synchronized to a sort of meshing relationship, so that the teeth of one engage the member alternately with the teeth of the other to offset portions of the member equal distances to opposite sides of the plane of its surfaces, such offset portions being spaced at regular intervals along each edge and alternating toone side and the other along the length of the edge.

The crimping rollers are so arranged that the sinuosities or crimps 15 which they produce are deepest at the edged the member and taper laterally inwardly therefrom to vanish at some predetermined distance from the edge. To this end the rollers can be slightly conical, as

Referring now more particularly to the accompanying drawings, the numeral 5 designates generally a cold roller formed heavy metal member of Z-section, intended for use as a purlin or the like, and having a substantially flat central web portion 6, a pair of main flange portions 7 bent from the web portion at substantially right angles thereto and projecting to opposite sides of the web portion, and a pair of outer flange portions 8, one for each of the main flange portions 7, each of said outer flange portions being bent inwardly from its main flange portion at an angle of about 45 thereto. The member 5 is cold roller formed from flat strip stock, typically of 12, 14 or 16-gage, and having a uniform width along its length. All bends in the member 5 are along lines parallel to its longitudinal side edges.

In forming member 5, the strip stock 10 (see FIGURE 3) is passed lengthwise, while cold, through conventional forming rollers 11, which bend it to the desired shape. It will be understood that complete formation of the member requires that the stock pass through successive sets of rollers 11, by which it is progressively bent to the desired final shape.

In imparting bends to the stock, the rollers 11 necessarily apply forces to the stock which stretch its edges, as at 12, to a greater extent than the central portion of the stock. As it emerges from the forming rolls, the piece therefore has a greater length adjacent to its edges than at its central web portion 6. The extra lengths of metal in the edge portions of the member impose stresses upon it all along its length, which stresses throw a curvature into each outer flange portion 8. Since those flanges lie at opposite sides of the web, the net effect of such stresses is to give the member a pronounced twist along its length, which twist is readily visible and in the case of a heavy gage piece would be but slightly less than as illustrated in FIGURE 1.

The present invention contemplates the foreshortening of the marginal edge portions of the mebmer 5 to bring their projected lengths into substantial equality with the length of the central zone or web 6 of the member, to thus relieve the unbalance of stresses about the axis of the member by which twist and curvature are produced. According to the invention, the foreshortening of the edge portions is accomplished by slightly crimping the member all along each of its side edges, so that as viewed edge-on from the side the member is very slightly sinuous or wavy in appearance.

Such crimping is most readily accomplished by means of cooperating gear-like crimping rollers 14 (see FIG- URE 4) through which the member can pass shortly after leaving the last set of forming rollers. The crimping rollers can either be rotatably driven by suitable power means (not shown), so that they propel the member shown, tapering away from the edge of the piece on which they operate, or they can be mounted with their axes converging slightly toward the edge of the member. The resultant tapering of the crimps or sinuosities of course compensates for the greatest excess length of the metal being at the very edge of the member.

In the case of a 12-gage Z-section channel having a width of about 8 /2 inches, excellent straightening was achieved with crimps having a total throw of about .03 inch as measured from the crest of one sinuosity to the bottom of the neXt opposite one. The crimps extended into the outer flange portions 8 for a distance between 25% and 50% of the width thereof. The presence of such slight crimping is of no consequence in most applications for which such a member would be employed.

Some slight experimentation may be necessary in any given case to determine the exact depth of crimping required to bring a member to perfect straightness, and for this reason the crimping rollers 14 are preferably so mounted that their shafts can be translatingly adjusted relatively toward and from one another and locked in any position of such adjustment. Once the correct adjustment is determined for a member of a given gage, width and shape, that adjustment can be maintained for all such members, whatever their lengths.

It will be obvious to those skilled in the art that for short-run production the crimping contemplated by this invention can be accomplished by means of a press having suitable serrated crimping jaws. It will also be evident that the crimps or sinuosities need not necessarily offset the edge portion of the member equal distances to opposite sides of the plane of its surfaces, so long as the offsets are at fairly uniform lengthwise intervals and are fairly uniform. in depth.

While the invention has been illustrated and described with particular reference to Z-section members, it will be understood that this is merely for purposes of example, and that the principles of the invention apply equally well, and in an obvious manner, to cold roller formed metal members of other shapes.

From the foregoing description, taken together with the accompanying drawings, it will be apparent that this invention provides a simple and inexpensive method of eliminating curves and twists from cold roller formed metal members produced from flat strip stock, and provides a cold roller formed member per se which is straight, true and untwisted all along its length.

What is claimed as my invention is:

1. The method of eliminating lengthwise curavature from an elongated structural member which is cold roller formed from uniform width strip stock to have bends along lines parallel to its side edges, which method is characterized by:

crimping the member along a marginal side edge portion thereof to provide small offsets out of the plane of the surfaces of the member at intervals therealong, which offsets are of substantially uniform amplitude along said edge and decrease in amplitude laterally inwardly from said edge, and by which offsets the metal along said edge is foreshortened to an extent which is greatest at said edge and progressively decreases to zero at a predetermined lateral distance from said edge.

2. The method of producing, from a substantially straight, flat strip of metal that is of uniform width along its length, a structural member which is bent along lines parallel to its side edges and is straight and untwisted along its length, which method comprises:

(A) passing the strip while cold through forming rollers by which it is preliminarily bent to the desired cross sectional shape; and

(B) thereafter crimping the member along an edge portion thereof to offset localized portions of the member out of the plane of the surfaces of the member at substantially uniform intervals along said edge, said localized portions being offset by the greatest amount at said edge of the member and tapering laterally inwardly therefrom, and cooperating to foreshorten the metal along said edge of the member to the extent necessary to copensate for the excessive length of said edge portion of the strip that resulted from the operation of the forming rollers.

3. The method of claim 2, wherein the crimping is occomplished by: passing the strip through crimping rollers.

4. An elongated cold roller formed metal structural member which is of substantially uniform width along its its length and which is bent along lines parallel to its side edges and has a substantially uniform cross sectional shape at all points long its length, said structural member being characterized by:

a crimp on the member extending along the length of one side edge thereof by which localized portions at substantially uniform intervals along said edge are olfset out of the plane of the surfaces of the member, said portions being offset by substantially uniform amounts all along said edge, and tapering laterally inwardly from said edge so that all offsets diminish that extend along lines parallel to the side edges of the member, which method is characterized by:

crimping the edge portion of the member to offset portions thereof from the planes of its surfaces and thereby foreshorten said edge portion to the extent necessary to compensate for its greater length.

'6. The method of removing undesired curves and twists from a metal structural member which is cold roller formed from uniform width strip stock to have bends that extend along lines parallel to the side edges of the member, which method is characterized by:

displacing localized portions of the member, adjacent to one edge thereof, out of the plane of the surfaces of the member, said localized portions being at substantially uniform intervals along said edge and displaced by substantially uniform amounts at said edge and by taperingly decreasing amounts laterally inwardly from said edge.

References Cited UNITED STATES PATENTS 702,836 6/1902 Weber 72168 464,403 12/1891 Turpin 72196 1,015,429 1/1912 Fahrney 72177 1,356,567 10/1920 Smith 72379 3,137,922 6/1964 Schumacher 72-701 RICHARD J. HERBST, Primary Examiner LOWELL A. LARSON, Assistant Examiner US. Cl. X.R. 

